The film grown-ups are the real life parents of the kids.
Over the course of the film the kids try to eat pizza in 3 occasions and every time something happens that prevent them from eating it.
Vero-Adult explains to the kids that the adults have spent their entire lives doing combat simulations to defeat the robots.
In the films opening, Javier is shown designing one of these simulations.
There is a scene that shows you all the movies that influenced the creation of TRAVELLERS. It is so subtle that if you blink you'll miss it. Just look at the decor in the dining room scene.
As a bonus, if you look at the monitors behind Javier's shoulders they are actually showing the movie TRAVELLERS.
As a bonus, if you look at the monitors behind Javier's shoulders they are actually showing the movie TRAVELLERS.
At the end of the film the kids became the new adults by deciding to help a new group of children (the 12-year old version of themselves) effectively completing the circle of life and re-starting it again.